1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of making the same, and more particularly, to a liquid crystal display device having the coupling effect improved and a method of making the same with five photolithographic and etching processes (PEPs).
2. Description of the Prior Art
Due to advantages of small size and low radiation, the liquid crystal display (LCD) has been the most popular display.
Referring to FIG. 1, FIG. 1 is a schematic diagram illustrating a top view of a pixel structure of an LCD according to a prior art. As shown in FIG. 1, two adjacent data lines 12 and two adjacent scan lines 14 define a pixel structure 10 of an LCD according to the prior art. Each pixel structure 10 comprises a thin film transistor 18 (TFT), a pixel electrode 20 and a common electrode 22. Referring to FIG. 2 together with FIG. 1, FIG. 2 is a schematic diagram illustrating a cross-section of the LCD along line AA′ of FIG. 1. The line AA′ is along the cross-section of the data line 12, and FIG. 2 shows the cross-section of two adjacent pixel structures 10. As shown in FIG. 2, the LCD of the prior art comprises a first substrate 24, a second substrate 32 and a liquid crystal layer 34 disposed between the first substrate 24 and the second substrate 32. A common electrode 22, a gate insulating layer 26 covering the common electrode 22 and the first substrate 24, a data line 12 disposed on the gate insulating layer 26, a passivation layer 30 covering the data line 12 and the gate insulating layer 26, and a pixel electrode 20 disposed on the passivation layer 30 are disposed on the first substrate 24 in sequence. The second substrate 32 comprises a black matrix 36 disposed on a side of the second substrate 32 opposite to the first substrate 24.
In each pixel structure 10, the pixel electrode 20 disposed above the common electrode 22 constitute a storage capacitor. In addition, light-leakage regions are at two sides of the data line 12. Therefore, besides being a bottom electrode of the storage capacitor, the common electrode 22 together with the black matrix 36 disposed on the second substrate 32 and corresponding to the data line 12 also can shield the light-leakage regions. However, a coupling effect will be generated between the pixel electrode 20 and the data line 12. If the coupling effect between the pixel electrode 20 and the data line 12 is desired to be avoided, a distance there between should be increased. With the increase of the distance, the light-leakage regions at the two sides of the data line 12 will be broadened, so that the widths of the common electrode 22 and the black matrix 36 should be enlarged to shield the light-leakage regions. Hence, the aperture ratio will be reduced. In design, the black matrix 36 is disposed on the second substrate 32, and the misalignment between the first substrate 24 and the second substrate 32 should be considered, so that the width of the black matrix 36 also should be further broadened. Therefore, in the condition without affecting the aperture ratio, how to reduce the coupling effect between the pixel electrode and the data line is an extremely important goal.